1. Field of the Invention
The present invention relates to a liquid discharge head mounted on a liquid discharge apparatus and a manufacturing method therefor.
2. Description of the Related Art
A liquid discharge apparatus, such as an ink jet printer, is a system wherein ink is discharged when bubbling is produced by thermal energy generated by an electrothermal transducing element, and can form and record high definition images at high speed. A common configuration used for an ink jet recording head (liquid discharge head) includes: multiple discharge ports, and flow paths that communicate with the discharge ports; and a plurality of electrothermal transducing elements that generate the thermal energy that is used for the discharge of ink. Each of the electrothermal transducing elements includes a heat resistor, and an electrode for supplying power to the heat resistor, that provides insulation between the electrothermal transducing elements. The ends of the individual flow paths on the side opposite the discharge ports communicate with a common liquid chamber, to which ink from an ink tank, which serves as an ink reservoir, is supplied and retained. The ink supplied to the common liquid chamber is introduced to the flow paths, and forms and maintains a meniscus near each of the discharge ports. In this state, when the electrothermal transducing elements are selectively driven, ink on a thermal acting face is rapidly boiled using the thermal energy that is generated, and ink is discharged by pressure associated with the status change.
In the ink discharge process, due to the heating of the heating resistor, the thermal acting portion of the head is exposed at a high temperature, and as the ink bubbles or shrinks, compositely sustains cavitation shock and a chemical reaction. Therefore, a second protective layer is deposited on the thermal action portion to protect the electrothermal transducing elements from cavitation shock and a chemical reaction due to ink. If the second protective layer is damaged or melted by cavitation shock or a chemical reaction, and the first protective layer is exposed to ink, the ink would soon contact the electrothermal transducing elements, so that the electrothermal transducing elements could be disconnected and lose the function of bubbling elements. Thus, the durability of the second protective element is used as one parameter to control the durability of the ink jet recording head.
It is known that, as ink bubbling is performed, the temperature on the surface of the second protective layer rises to around 700° C., for example. Thus, layer characteristics that are superior to heat resistance, mechanical properties, chemical stability, oxidation resistance and alkali resistance are requested for the second protective layer that contacts ink. An example material conventionally proposed for the second protective layer is a precious metal, a high boiling transition metal or an alloy of them, a nitride, a boride, a silside or a carbide of these metals, an amorphous silicon or an amorphous alloy.
Above all, a precious metal is chemically stable, and can cope with ink that is improved on in the future, e.g., ink that is improved on to prevent bleeding (smearing between ink of different colors), or to increase color development or water repellency in consonance with a high image quality. There is a case wherein, when ink is employed that contains, for example, divalent metallic salt, such as Ca (calcium) or Mg (magnesium), or an element for forming a chelate complex, the second protective layer is easily corroded due to thermal reaction with the ink. A second protective layer formed of precious metal is expected to be especially effective for ink that provides such a chemical reaction.
When a precious metal is employed as the second protective layer for an ink jet recording head, the deposition of an adhesive layer made, for example, of titanium or chromium, between the first and second protective layers, is proposed in Japanese Patent Application Laid-Open No. H05-301345. Further, as proposed in Japanese Patent Application Laid-Open No. H05-096734, in order to securely fix a flow path formation member made of an organic material to the second protective layer of the ink jet recording material, oxidization, or a coupling process, is performed for the surface of the second protective layer to increase adhesion.
Additionally, to cope with an increase in accuracy and density, the arrangement disclosed in Japanese Patent Application Laid-Open No. H09-057985 has become popular, i.e., a ceiling portion that includes flow paths and discharge ports is formed by spin coating or the patterning of a resin. According to this arrangement, as described in Japanese Patent Application Laid-Open No. H11-348290, the adhesion of the flow path formation member to the substrate is a problem. Thus, an adhesive resin layer made of a polyether amide resin is arranged between the flow path formation member and the substrate.
As additional proposals, in Japanese Patent Application Laid-Open No. 2002-248771 (U.S. Pat. No. 6,676,241), an adhesive layer is deposited in an area, larger than a bonded face, where stress is concentrated, and in Japanese Patent Application Laid-Open No. 2002-326361 (U.S. Pat. No. 6,953,530), tiny pits are formed in the adhesive portion of a substrate, and anchor effects that increase the adhesive force are thus obtained.
FIGS. 7 and 8 are a partial plan view and a partial cross-sectional view of the arrangement of an ink jet recording head disclosed in Japanese Patent Application Laid-Open No. 2002-248771. For this ink jet recording head, multiple flow path walls 113 and a ceiling portion, in which discharge ports 111 are formed, are provided by employing a flow path formation element 110 made of a resin. The discharge ports 111 are open, opposite each other, above multiple heating resistor layers 102 deposited on the substrate 101. The multiple flow path walls 113 are shaped like the teeth of a comb, and form flow paths for introducing ink, supplied by an ink flow path 112, to the individual electrothermal transducing elements. At the entrance of each flow path, two pillars 114 are located at a predetermined interval and extended perpendicularly in order to prevent dust from entering the flow path.
The flow path formation member 110 is bonded to the substrate 101 by an adhesive resin layer 108 made of a polyether amide resin. That is, the adhesive resin layer 108 is formed between the flow path formation member 110 and the substrate 101.
However, the present inventor found through study that when the second protective layer is formed of a precious metal, adhesion should be promoted with an organic material member that is overlaid.